Abstract
Starting from methyl 2-hydroxy-4-methoxy-6-methylbenzoate (6 ) and its regioisomeric dehydrodimers 7 -9 ,readily available by an oxidative coupling reaction of 6 , the naturally occurring coumarins siderin(1 ), kotanin (2 ),isokotanin A (3 ) and desertorin C (4 ) were synthesized in a novel and highlyefficient three-step transformation. In the case of kotanin (2 ) both atropisomers were prepared fromthe pure atropisomers of 7 .
Key words
atropisomerism - biaryls - oxidative phenoliccoupling - natural coumarins
References
1 Bringmann G.
Günther C.
Ochse M.
Schupp O.
Tasler S.
Prog.Chem. Org. Nat. Prod.
2001,
82:
1
2 Stothers JB.
Stoessl A.
Can. J. Chem.
1988,
66:
2816
3a Büchi G.
Luk KC.
Kobbe B.
Townsend JM.
J. Org.Chem.
1977,
42:
244
3b See also Refs.
[2 4b 7a
4a Laakso JA.
Narske ED.
Gloer JB.
Wicklow DT.
Dowd PF.
J.Nat. Prod.
1994,
57:
128
4b Nozawa K.
Nakajima S.
Kawai K.-I.
Udagawa SI.
Miyaji M.
Phytochemistry
1994,
35:
1049
5 Nozawa K.
Seyea H.
Nakajima S.
Udagawa SI.
Kawai KI.
J. Chem. Soc., Perkin Trans. 1
1987,
1735
1 ):
6a Venturella P.
Bellino A.
Piozzi F.
TetrahedronLett.
1974,
15:
979
6b Chexal KK.
Fouweather C.
Holker JSE.
J. Chem. Soc., Perkin Trans. 1
1974,
554
6c Ahluwalia VK.
Kumar D.
Indian J. Chem.,Sect. B
1976,
14:
589
2 )
7a Racemic : Büchi G.
Klaubert DH.
Shank RC.
Weinreb SM.
Wogan GN.
J.Org. Chem.
1971,
36:
1143
7b Stereoselective : Lin G.-Q.
Zhong M.
Tetrahedron:Asymmetry
1997,
8:
1369
3 )
8a Racemic : Lin G.-Q.
Zhong M.
Acta Chim.Sin.
1997,
55:
97 ; Chem. Abstr. 1997 , 126 , 211942
8b Stereoselective : Lin G.-Q.
Zhong M.
TetrahedronLett.
1996,
37:
3015
8c Stereoselective : Bringmann G.
Hinrichs J.
Henschel P.
Kraus J.
Peters K.
Peters E.-M.
Eur.J. Org. Chem.
2002,
1096
4 )
9a Racemic :
Rizzacasa MA.
Sargent MV.
J. Chem. Soc., PerkinTrans. 1
1988,
2425
9b Stereoselective:
Kyasnoor RV.
Sargent MV.
Chem. Commun.
1998,
2713
9c Steroselective : Baker RW.
Kyasnoor RV.
Sargent MV.
Skelton BW.
White AH.
Aust.J. Chem.
2000,
53:
487
10 The total syntheses of the three biarylcoumarins 2 -4 require ca.25 steps according to the literature.
11a Drochner D.
Hüttel W.
Nieger M.
Müller M.
Angew. Chem.Int. Ed.
2003,
42:
931 ; Angew. Chem. 2003 , 115 , 961
11b Drochner, D.; Karl,U.; Nieger, M., Müller, M.; Steglich, W., manuscript inpreparation.
12 6 ., e.g.: Connor DT.
Sorenson RJ.
J. Heterocycl. Chem.
1981,
18:
587
13 Long RS.
J.Am. Chem. Soc.
1947,
69:
990
14 Basi W.
Polish J. Chem.
1995,
69:
376 ; Chem. Abstr.
1995 , 123 , 32908
15 Szabó V.
Borda J.
Theisz E.
ActaChim. Acad. Sci. Hung.
1980,
103:
271 ; Chem. Abstr. 1981 , 94 , 103116
16a Suzuki E.
Katsuragawa B.
Inoue S.
Synthesis
1978,
144
16b 17 This was demonstrated for the 6,8′-bisaminochromenone 15 , which was converted to desertorin C(4 ) in a single step. Hence, the hydrolyticmixture was dehydrated chemically with dimethyl carbonate afterno starting material could be detected (TLC). Acetyl chloride wasadded to generate additional HCl. The yield (34%) is comparableto the overall yield of the two-step procedure (36%).
18 The low yield in the case of M -(-)-2 ismainly due to a nonoptimized reaction time for acidic hydrolysis.
19 The isomers of kotanin(2 )were erroneously mismatched in a previous publication.
[11a
20a Chiarello J.
Joullié MM.
Tetrahedron
1988,
44:
41
20b Sala T.
Sargent MV.
J. Chem. Soc., Perkin Trans.Trans.1
1981,
855
21 Crystallographic data (excluding structurefactors) for the structures reported in this paper have been depositedwith the Cambridge Crystallographic Data Centre as supplementary publicationno. CCDC-215646. Copies of the data can be obtained free of chargeat www.ccdc.cam.ac.uk/conts/retrieving.html [orfrom the Cambridge Crystallographic Data Centre, 12 Union Road,Cambridge CB2 1EZ, UK; Fax: int. code+44-1223/336-033;e-mail: deposit@ccdc.cam.ac.uk].
